R-f sputtering apparatus

ABSTRACT

The radio frequency generator of a sputtering system is inductively coupled to a sputter target to achieve radio frequency power transfer and impedance matching between generator and target. The radio frequency generator assembly containing the primary winding of a radio frequency coupling transformer is adjustably positioned over the secondary winding of this transformer, which is disposed in juxtaposition to the vacuum enclosure and to the sputter target container therein, to achieve sputtering. The inductive coupling allows impedance matching through varied degrees of coupling between the primary and the secondary coils, thus eliminating need for a radio frequency transmission line and associated impedance matching devices between frequency generator and the sputter target. This reduces the total volume required for the radio frequency components; it simplifies the operation; and eliminates the danger of radio frequency radiating from a mismatched cable connection.

BEST AVAILABLE COPY July 25, 1972 g ss m 3,679,571

3-}? SPU'ITERING APPARATUS Filed Oct. 12. 1970 4 Sheets-sheaf. 1

INVENTOR.

[Mi-T 4: I A'IiRNEYS BEST AVAILABLE COPY July 25, 1972 F. H. ENSSLIN R-FSPUTTERING APPARATUS 4 Sheets-Sheet 2 Filed Oct. 12, 1970 FIG'. 4

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FRIEDER H. ENSSLIN 7 04 I ATTORNEYS Xv BEST AVAILABLE c July 25, 1912 FYF. H. ENSSLIN v 3,679,571

R-F SPU'ITERING APPARATUS Filed Oct. 12, 13 70 4 Sheets-Sheet 5INVENTOR. FRIEDER HIENSSLIN W454... La

ATTORNEYS BESI AVAILABLE COPY July 25, 1972 F. H.'EN$SLIN R-FSPU'I'TERING APPARATUS Filed Oct. 12, 1970 4 Sheets-Sheet 4 FRIEDER H.ENSSLIN ATTORNEYS United States Patent 3,679,571 R-F SPUTTERINGAPPARATUS Frieder H. Ensslin, Rochester, N.Y., assignor to The BendixCorporation, Rochester, N.Y. Filed Oct. 12, 1970, Ser. No. 80,068 Int.Cl. C23c 15/00 US. Cl. 204-298 23 Claims ABSTRACT OF THE DISCLOSURE Theradio frequency generator of a sputtering system is inductively coupledto a sputter target to achieve radio frequency power transfer andimpedance matching between generator and target. The radio frequencygenerator assembly containing the primary winding of a radio frequencycoupling transformer is adjustably positioned over the secondary windingof this transformer, which is disposed in juxtaposition to the vacuumenclosure and to the sputter target contained therein, to achievesputtering. The inductive coupling allows impedance matching throughvaried degrees of coupling between the primary and the secondary coils,thus eliminating need for a radio frequency transmission line andassociated impedance matching devices between frequency generator andthe sputter target. This reduces the total volume required for the radiofrequency components; it simplifies the operation; and eliminates thedanger of radio frequency radiating from a mismatched cable connection.

The present invention relates to radio frequency sputtering apparatus.In such apparatus an ionizing discharge is employed in a controlled gasatmosphere to bombard a negatively biased material with positivelycharged gas ions.

The sputtering of dielectrics from a dielectric target cannot beaccomplished solely by negatively biasing the target, because a positivesurface charge caused by initial ion bombardment collects on the targetsurface inhibiting further bombardment by positive ions. Therefore,dielectrics can only be sputtered when some means is provided toneutralize the positive charge built up by positive ion bombardment.This has been done heretofore by application of a high-frequencyalternating current to the target to be sputtered. Thus, it is possibleto neutralize the positive surface charge by electrons attracted to thetarget during each positive half cycle of the RF wave so that the targetmay be sputtered again by ion bombardment during the next negative halfcycle. Generally RF power dissipated by the target makes it necessary tocool the target and target support, to maintain the target a a properoperating temperature. Prior attempts at cooling ion targets haveresulted in quite complicated and electrically ineificient structure.

One of the main problems encountered with RF sputtering is eflicientcoupling of power from the RF power supply to the RF target via fixedimpedance transmission lines.

Heretofore, radio frequency generating systems for sputteringdielectrics have included an RF generator, a first impedance matchingcoupling device, an RF transmission line or cable, a second impedancematching coupling device, and an RF electrode target, capacitivelycoupled or directly connected to the second coupling device. Theimpedance of commercially available RF cables does not exceed therelatively low value of 300 ohms while the output impedance of the RFamplifier anode circuit is in the kilo-ohm range. The RF energy hastherefore to be transmitted through such a cable to the sputter targetwhere a matching network brings the impedance from the low impedance ofthe cable back up into the kilo-ohm range ice of the sputter target. Anymismatch between the RF amplifier output and the RF cable and/or betweenthe RF cable and the target creates power losses; and even the mostcarefully designed matching networks have power losses. These lossesheat up the cable and make it radiate RF energy just as if it were anantenna, both very undesirable eifects. Radio frequency radiation fromthe RF cable always exists to some degree in practice.

Also the number of components required in the networks is high; andsince these components are variable inductors and variable capacitorsrequiring high voltage ratings, they are expensive and space consuming.Heretofore, the RF amplifier tubes have been cooled by forced air or byconvection; but the sputter target was water cooled. Further, the watercooling of the target necessitated elevation of the cooling water fromground potential to the RF target potential and back to ground. This isgenerally done by conducting the water through two coiled lengths ofinsulating tubing, which requires space within the shielded box of thematching network to keep the coils from radiating RF frequency.

The primary objects of this invention are to eliminate RF power losses,to increase the overall efficiency, to reduce the number of componentsin the power supply, and to provide a unit much more compact than knownR-F sputtering apparatus.

Another object of the invention is to provide a unit of the characterdescribed with which the radiation of RF energy is reduced to negligiblelevels.

Another object of this invention is to eliminate the radiation of radiofrequency into space even under conditions ,of extreme mismatch betweenthe components.

Another object of the invention is to provide a unit of the typedescribed in which low voltage breakdown components may be used.

A further object of this invention is to provide a single structure thatfunctions as a radio frequency coupling device, an ion target support,and a means for conducting a coolant to cool the ion target and iontarget support during the presence of radio frequency energy in thestructure.

Further objects of the invention are to provide a water cooling systemfor a unit of the character described in which both water inlet andwater outlet may be at ground potential and which lends itself toreduction of the size of the RF generator.

The above and other objects of the invention will be apparenthereinafter from the following description and from the recital of theappended claims particularly when read in conjunction with theaccompanying drawings.

Several diiferent embodiments of the invention are illus-- trated in theaccompanying drawings wherein:

FIG. 1 is a diagrammatic view of sputtering apparatus made according toone embodiment of this invention;

FIG. 2. is the schematic diagram of a preferred circuit embodiment ofthe RF generator, inductive coupling device and RF target electrode;

FIG. 3 is a fragmentary sectional view taken at right angles to the viewof FIG. 1 and showing that the RF sputtering apparatus has a coilmounted entirely outside the evacuable enclosure;

FIG. 4 is a diagrammatic view illustrating a further embodiment of theinvention;

FIG. 5 is a longitudinal section taken on the line 5--5 of FIG. 6showing a preferred construction of RF generator;

FIG. 6 is an end view of this generator;

FIG. 7 is a longitudinal section showing a preferred form of targetmounting and the means for supplying current to and for cooling thetarget; and

FIG. 8 is a fragmentary section on the line 88 of FIG. 7, looking in thedirection of the arrows.

v In the apparatus of the present invention the radio frequency powersupply is mounted directly on the sputter conventional components on aseparate chassis. This chassis is then mounted on insulators and latchedto ground by a capacitor. p v

The invention is characterized by a sputtering apparatus having a-radiofrequency generator inductively coupled to RF electrode target inside anevacuable enclosure. The RF electrode target includes a coupling coilmounted on the outside of the enclosure with one end of the coil coupledto the target. The RF electrode target coil is fabricated from a conduithaving two passages for conveying a coolant through the coil to and fromthe target. j Referring now to the drawings by numerals of reference andfirst to FIG. 1, denotes the evacuable enclosure of a sputteringapparatus. A vacuum pump system 11' is connected to the enclosure 10through an inlet 12; and a'source of gas 14, preferably argon, isconnected to the enclosure through a valve and duct 16.

Mounted outside the enclosure is an inductor 20. The inductor20comprises two helical coils 21 and 22 wound one upon the other. Thecoils are wholly outside the enclosure which has an opening 18 in itswall 17, on the inside of which is mounted a ring 35 of a suitableinsulating material such as, for instance, a ceramic. The ring insulatesthe coil from the enclosure 10 and supports the ion target 23(preferably in the form of a plate of materialto be sputtered) in afixed position. This assembly is the RF electrode target support 24. Thering forms, with the opening 18 in the enclosure wall 17, a recess inwhich the coils 21 and 22 extend intooperative proximity to the target.

Ordinarily it is necessary to cool the target. The inductor 20-,including the coils 21 and 22, is therefore fabricated from anelectrically-conductive tubular conduit connected to a coolant pumpingsystem 25, which may be the same as the coolant pumping systems for theinductor 30 and primary coil 42 which will be described hereinafter.

Directly opposite the first inductor 20 in the embodiment shown is asecond inductor 30,,similar to first inductor 20, andcomposed of twohelical tubes 31 and 32 wound one upon the other. This inductor 30 isconstructed to hold or support the substrate 33 (preferably a plate ofmaterial to be coated). The assembly is the RF electrodesubstratesupport 34.

The substrate, support is disposed so that when the target 23 and thesubstrate 33 are in position, the material, which is sputtered from thetarget 23, impinges on the substrate 33 to form a coating thereon. I pThe coils 31 and 32 extend through an opening 39 in the wall 27 of theenclosure 10 and are insulated from the enclosure by the insulator 36,which isring shaped and surrounds the coils so as to form in effect arecess into which the ends of the coils extend. The substrate support.34 itself seals the enclosure so that inductor 30, like inductor 20,lies wholly outside the enclosure.

The inductor 30 is an adjunct to the structure shown in FIG. 1. It maybe omitted if desired. It is supplied for etching from the substrate orfor biasing the substrate.

The radio frequency generator assembly 40 includes a primary coil 42(FIG. 2) for inductively coupling an RF generator 43 to target coil 20and/or substrate coil 30 (FIG. 1) to transmit radio frequency energy tothe inside of said enclosure.

' FIG. 2 is a schematic diagram of a preferred circuit embodiment of theRF generator associated with the RF generator assembly 40 mounted on theenclosure 10.

The preferred amplifier design is one in which the anodes of theamplifier tubes 50 (FIG. 2), of which four are shown in FIGQ'2, are atDC" ground potential with the cathodes at a negative potential withrespect to ground, so that the primary coil 42, which is electricallyconnected to the anodes, is also at DC ground potential; This eliminatesthe need for electrically, insulating the tubing of the coil 42 toprevent inadvertent grounding of the circuit through the coolant,connecting tube to the water source and drains I The preferred RFgenerator includes a push-pull, Class C amplifier, using amplifyingtubes 50 whichare pref erably tetrodes (type 8072) which receiveoscillations of preferably 13.56 megahertz, from the oscillator 52,preferably, a' pentode (type 5763). However, in some applications asingle tube amplifier may be used. A cathode power supply 54, filamentpower supply 56,-bias power supply 58, screen power supply 60, and theoscillator 52 are preferably located outside the generator assembly sothat the assembly may be a small and compact unit. I

Resistors 62, 64, 66 and 68, inductors 70, 72, and switch 74 are part ofthe circuit thatcouples the amplifier tubes 50 to the oscillator 52, andprovides for the selection of different numbers of tubes 50 fordifferent output power levels.

Since the RF generator 40 is variably inductively coupled to the coil 20of the RF target support 23 or to substrate coil 30, stepless impedancematching is obtained.

The capacitors 29, 75, 76, 77 are in circuit relationship with theirrespective coils 42, or 20 (30) to tune the circuits to their resonantfrequency.

, To cool the anodes of the RF amplifier tubes 50, the tubes 50 aresealed with O-rings into metal blocks 80, which permit the passage of acoolant, for example, water. In the preferred arrangement, both theanodes of tubes '50 and the coil 42 are cooled by a coolant which entersthe coil 42 to 82, flows through the coil 42 into the blocks 80 inconduits 84 and 86, out of the blocks 80 through conduits 87 and 88,through the coil 42 again and out through the conduit at 89. The coppertubes 84, 88, 86, and 87, which form the anode end of the coil 42,connect at the water inlet and water outlet to the metal blocks 80 whichhave cavities machined in them to provide smooth flow of water over theexterior of the amplifier tubes 50. Conduits 82 and 89 may be connectedto a pump or to a cooling water supply.

Similarly, the RF electrode-target support 24 and the RFelectrode-substrate support 34 are cooled.

The type of amplifier preferred is a push-pull Class C amplifier usingfour tubes of the type 8072 in parallel and driven directly by a crystalcontrolled oscillator having one tube, type 5763. Two considerations ledto the used parallel tubes in the final amplifier. First, six tubes oftype 8072, connected as two pairs of three tubes in parallel with theirassociated components, is considerably more economical than a single,pair of larger tubes capable of the same output. Secondly, parallel tubeoperation permits the selection of any desired number of tubes inparallel to vary the output power of RF amplifier without affecting theoutput voltage or making it necessary to change the turns ratio of thecoupling transformer or other impedance matching means to adapt thepower supply to a diiferent size target. The selection of difi'erentnumbers of tubes in parallel is accomplished by heating only thefilaments of the tubes required for the desired output power level. Thedesired number of tube filaments maybe selected by a switch which alsoselects the values of the screen and grid resistors to maintain propergrid and screen currents for any tubes in operation. The same switchmayalso be used to change the sensitivity of an overload relay [for theanode power supply. This relay senses the anode current and deenergizesthe anode power supply in case of an overload. This makes the overloadcurrent, which would turn off the anode power, afunction of the numberof tubes in operation at that time.

Since inductive coupling is employed, a push-pull type amplifier ispractical. This has the additional advantage that no even harmonics aregenerated and that push-pull amplifiers work at a higher level ofefliciency. Inductive coupling then allows stepless impedance matchingwithin a certain range by varying the inductive coupling be tween the RFamplifier tank coil 42 and the coupling coil 20 of the sputter target.To facilitate such variable coupling, the complete RF amplifier box 43(FIG. 2) may be mounted on a track allowing it to slide over the targetcoupling coil 20. In FIG. 1, the radio frequency generator 40 is movablymounted by means of rollers 90 and tracks 92 on enclosure so that thecoils of the HF generator may be coupled to the coil 20 to transmit RFenergy to the target 23.

In operation, after the enclosure 10 is evacuated by pump 11, a smallamount of argon gas from source 14 is allowed to enter the enclosure 10.The argon gas is then ionized by application of radio frequency energytransmitted to the target 23 inside the enclosure. This draws positiveions to the target 23 during each negative half cycle of the RF wave,causing ions to impinge upon the target 23 and sputter material onto thesubstrate 33. During the sputtering process the coolant pumping systemcirculates coolant through the coil 20 to cool the target. Similarly,the substrate 33 may also be cooled by circulation of water through coil30.

To transmit radio frequency energy to the target surface 23 so that itmay sputter material on the substrate 33, the target holder isinductively coupled to the radio frequency generator 40. Adjustment ofthe radio frequency generator 40 relative to the enclosure 10 allowsvariation in the inductive coupling of the radio frequency generator tothe target. This variable inductive coupling eliminates the need for animpedance matching network to obtain maximum transfer of RF energy tothe target 23.

The coil 30 permits sputtering the surface of the substrate whendesired, for example, when cleaning the surface of the substrate and/orpreparing the substrate surface so that the coating bonds better.

The embodiment of the invention illustrated in FIG. 4 discloses how boththe target and a single tube amplifier can be cooled using a single pairof helically wound coils. Here the target is indicated schematically at23. 50' is the amplifier tube. The copper cooling coil is denoted at100. The water enters this coil at 101, and the coil is helically woundon itself, and delivers the cooling water into the block 80' which ismachined with a cavity to provide smooth flow of water over the anode ofthe amplifier tube 50'. The water flows out of the block 80' to the tube102 which is helically wound on the tube 100, and which is coiled onitself as denoted at 103 and goes to the back of the target support, andthen is coiled on itself again and flows out of the tube at 104.

The cathode power supply of the tube is denoted at 54', the filamentpower supply at 56', the grid bias power supply at 58', and the screenpower supply at 60'. The oscillator or RF drive is denoted at 52. Theconnections between the various components may be similar to thosedisclosed in FIG. 2. The various elements of the tetrode 50' areconnected to capacitors 105 which in turn are connected to ground. Theinductor 72 forms part of the circuit that couples the oscillator 52' tothe amplifier tube 50'. The variable capacitors 75' and 77' permittuning the circuit.

In this embodiment of the invention, as in the previously describedembodiment, all operating power supplies for the radio frequencygenerator are located in a control cabinet away from the radio frequencygenerator; the target is inductively coupled to the radio frequencyamplifier; the coupling coil consists of the two copper tubes which areelectrically connected in parallel to form a twin tube, of which one,100, serves as the water supply and the other, 102, as the water drainfor the target and tube cooling water. Both the water supply 6 and drainconnections are at the RF grounded end of the double coil and areconnected to ground through a large capacitor 105. This eliminates theneed for having coiled up insulating tubing for the cooling Water supplyand drain inside the shielding enclosure.

The amplifier tube anode operates at DC ground potential, and thecathode is connected to a corresponding negative potential with respectto ground. Again, this per mits connecting the radio frequency groundedend of the tank coil or anode resonance coil of the radio frequencyamplifier directly to DC ground. The grounded end of the resonance coilis soldered directly against the wall of the shielding case of the radiofrequency amplifier for the purpose of cooling the whole amplifierenclosure.

With a single ended amplifier nearly half of all components required fora push-pull amplifier can be eliminated and an even better shieldedcoupling junction between the RF power supply and target can beprovided. It is also possible to reduce the size of the RF power supply.

In FIGS. 5 and 6, a presently preferred RF amplifier tube mounting andgenerator is shown. Here the amplifier tube is denoted at 110. The tubeis mounted in a housing 116 by means of a gasket 112 and a nut 114,which threads onto the tube. Housing 116 is secured to a slottedcylinder 117 that forms one electrode of the tank circuit capacitor. Theother electrode of this capacitor is formed by the outer shield can orhousing 118. The coil of the tank or anode resonant circuit is mountedinside,

the slotted cylinder.

The slot 119 (FIG. 6) in this cylinder has a double function. One is toprevent it from becoming a short circuit winding around the tank coiland the other is to provide spacing between this capacitor electrode andthe cooling coil tubing 120 which runs up along the inside of the outershielding can 118.

The final RF amplifier tube is mounted inside of a screen piston whosewall is denoted at 122. This piston allows the whole inner assembly toslide up and down inside the outer shield can 118. It is insulated fromthis can by the insulating sheet 123. This sheet, which is made ofTeflon, provides both insulation for the screen potential and smoothtravel for the piston inside the shield case 118.

The top cover 124 for the housing 118 is press-fit into this housing;and a nut 126 in the center of this cover, which threads on the tuningstud 128, serves as a means for adjusting the frequency of the innerresonant circuit. The plate 136, juxtaposed to the cover 124, isspring-loaded against the cover 124 by the tuning spring 132. The springstrap 134 serves to ground the connector mounting plate 136 to theflange of cover 124. The connector itself between the plate 136 and thecover 124 is denoted at 138.

Further chokes 140 are provided for all cables interconnecting the finalRF power supply with its auxiliary power supply for screen grid andfilament. The grid drive coil of this tube is denoted at 142. It iswound on the coil spacer sleeve 144 which slides on the stud 146. Thegrid drive capacitor is denoted at 148. The manifold, through which thecooling water is admitted, and out of which it drains, is denoted at150. The anode resonant coil 120 is mounted by means of the flange 152on the housing 116 for the amplifier tube.

A screen piston is provided which comprises disc 133 and wall 122. Thewhole assembly 122, 133, 136 125, 146, etc. slides on the insulatingsleeve 123 inside the can 118. Since one end of the tank coil isconnected to the outer shield can 118 and the other end is connected tothe anode of the final RF amplifier tube mounted on the inner assembly,the sliding movement effected by the screen piston extends or contractsthe length of the anode resonant coil 120 and thereby tunes thefrequency of the anode resonant circuit.

7 FIGS. 7 and 8 inconjunction with FIG. 4 show the presently preferredstructure of the evacuable enclosure and of the elements containedtherein;

17 again denotes one wall of the enclosure; and 160 is the target plate.The target is secured by screws or dowels 162 to a ceramic insulatingring 164. A Teflon insulator ring 166 surrounds ring 164 and is fastenedin .any suitable manner to the target plate 160 and wall 17. Theinsulator ring 164 itself is fastened to a clamp plate 168 by adjustingscrews 170 and clamp plate 168, in turn, is secured by screws 172 to thecan 40.

A variable capacitor 77' is secured by screws 174 to a plate 176, which,in turn, is fastened by screws 178 to target plate 160. The tubular coil103 is brazed or otherwise secured to the plate 176 and wound aboutcapacitor 77'. Capacitor 105 is connected by strap 180 and screw 182 tothe flange 184 of capacitor 77 A shaft 186, which passes through onewall of can 40', serves as a feed shaft for the capacitor 77'.

There is a ring 190 fastened in the open end of can 40'. This ring actsas a guide for the can 118 which telescopes into it and which isadjustably supported bemm the lower end of ring 190 by studs 197, whichthread into the flange 198 of the can and project upwardly foradjustment by knurled nuts 195 whose hubs seat against the lower face ofthe flange 196 of ring 190. Adjustment of the can 118 in ring 190effects impedance matching between the coil of the RF generator and thetarget; whereas the adjustment of the screen piston 122 (FIG. in the can118 elfects tuning.

One of the advantages of the DC grounded anode design for the finalradio frequency amplifier is that no DC is superimposed on the radiofrequency potentials applied to the components in the anode circuit.This preventsdestructive DC arc-over from occurring following a possibleradio frequency arc-over. For this reason, the voltage rating of thesecomponents is lower, and they are therefore smaller. Also the unpluggedunit only exposes grounded components making it very'safe to handle.

In comparing this radio frequency power supply design with conventionalradio frequency power supplies nsed for. sputtering, it was found that avolume reduction of approximately 1 to 5 was achieved.

When an all-metal vacuum chamber is used for sputtering with this radiofrequency amplifier, it is nearly impossible to detct any radiated radiofrequency energy.

Additional advantages of the DC grounding of the anode of the final RFamplifier are, as stated, that the inlet and outlet for the target andthe RF amplifier anode cooling water are located at the grounded end ofa double helical coil which comprises the RF transformer. Loops at theanode and target terminals feed the cooling water to the final RFamplifier anode andto the sputter target. No DC potential is present onthe compound of the RF output resonant circuit. This decreases theinsulation requirements of all components and makes it possible to mountone side of al components to ground. The danger of DC arcs developingafter RF does not exist. Water cooling of the final RF amplifier anodeincreases the power handling capability of a smaller tube, making a verycompact design possible. Furthermore, RF power transmission losses areeliminated. This, in itself, allows use of a smaller unit.

No RF matching network and no transmission line is needed. This alonesaves approximately 30% of the total required space. The majority ofcomponent failures is known to have occurred in these two components inolder RF units. It is estimated that approximately 70% of all repaircost and maintenance on the RF power supply can be eliminated with thepresent design. RF radiation to the outside is completely avoided sincethere is no more mismatched cable between units.

The final amplifier tube is water cooled which increases itspowerhandling capabilities, allowing the use of a low price and readilyavailable tube type.

stood that it is capable of further modification, and that thisapplication is intended to cover any modifications or embodiments of theinvention coming within the present disclosure and the recital of theappended claims.

Having thus described my invention, what I claim is:

1. Sputtering apparatus comprising an evacuatable enclosure,

a target support in said enclosure for holding a target of material tobe sputtered by ion bombardment,

an induction coil mounted outside but on said enclosure and having ahelical winding connected to said target support and constituting thesecondary winding of a radio frequency coupling transformer, wherebyupon operation of said transformer radio frequency energy is transmittedby said coil into said enclosure,

a primary coil also mounted outside said enclosure and having a helicalwinding and positioned in operative relation to said secondary windingso as to be inductively coupled to said induction coil, and

means mounted externally of said enclosure and oper:

able to develop a radio frequency signal in said primary coil to efiectoperation of said transformer.

2. Sputtering apparatus as claimed in claim 1, having means mountingsaid primary coil to be adjustable toward and away from said secondarycoil for impedance matching.

3. Sputtering apparatus as claimed in claim 2, wherein each of saidcoils comprises a plurality of convolutions, and means is provided foradjusting the convolutions of said primary coil toward and away from oneanother to effect tuning. Y

4. Sputtering apparatus as claimed in claim 1, wherein at least one ofsaid coils is electrically conductive tubing for conveying a coolant.

5. Sputtering apparatus as claimed in claim 4, wherein said secondarycoil is electrically conductive tubing for conveying a coolant to coolsaid target support.

conveying coolant.

7. Sputtering apparatus comprising an evacuatable enclosure having anopening in one wall thereof, an insulating member surrounding saidopening and forming therewith a recess in said wall and constitutingmeans for supporting a target in said enclosure, means for generating aradio frequency signal, includ ing a radio frequency couplingtransformer comprising a primary helical winding and a secondary helicalwinding, said secondary winding being disposed in said recess insidesaid target support but outside said enclosure, and said primary windingbeing also disposed outside said enclosure but being inductively coupledto said secondary winding. 8. Sputtering apparatus as claimed in claim7, wherein a housing is mounted slidably on said enclosure, and saidprimary winding is disposed in said housing, and having means forslidably adjusting said housing relative to said enclosure to match theimpedances of said signal generating means and said enclosure. 9.Sputtering apparatus as claimed in claim 8, wherein said primary windinghas a plurality of convolutions and means is provided in said housing toadjust the spacing of successive convolutions of said primary winding totune the radio frequency.

10. Sputtering apparatus as claimed in claim 7, wherein said windingsare electrically conducting tubular helical coils for conveying coolant.

9 11. Sputtering apparatus comprising an evacuatable enclosure, a targetsupport in said enclosure, a housing,

in means is provided for varying the inductive coupling between the twowindings.

17. Sputtering apparatus comprising an evacuatable enclosure,

a radio frequency generator and a primary transformer a target supportin said enclosure,

coil coupled thereto and mounted in said housing, a first inductormounted outside said enclosure but in the secondary coil of saidtransformer being mounted operative relation to said target support,

outside said enclosure and inductively coupled to a substrate support insaid enclosure, said primary coil, and being operatively connected asecond inductor mounted outside said enclosure but to said targetsupport to transmit RF signals into 10 in operative relation to saidsubstrate support, said enclosure upon operation of said generator, asource of RF signals for said inductors including a means for varyingsaid inductive coupling, primary transformer coil, and said secondarycoil comprising a double winding of means for inductively variablycoupling said primary helical electrically-conductive tubing, coil tosaid first inductor to transmit said RF signals an inlet for supplying acoolant to one of said windings via said first inductor to saidenclosure.

to cool said support, and 18. Sputtering apparatus as claimed in claim17, wherean outlet for draining the coolant from the other of in bothsaid inductors are electrically conductive tubes for said windings,conveying coolant to said target support and said subboth said inlet andsaid outlet being at ground strate support, respectively. potential. 19.Sputtering apparatus comprising 12. Sputtering apparatus comprising anevacuatable enclosure, an evacuatable enclosure, a target support insaid enclosure, a target support in said enclosure, a radio frequencygenerator mounted outside said ena housing, closure, a radio frequencygenerator and a primary transformer 5 a second enclosure mounted on thefirst-named coil coupled thereto and mounted in said housing, enclosure,the secondary coil of said transformer being mounted said generatorhaving an electronic amplifier tube,

outside said enclosure but in operative relation to a primarytransformer coil mounted in said second ensaid enclosure and inductivelycoupled to said closure and electrically connected to said tube, primarycoil to impart RF energy to said enclosure a block in said secondenclosure in which at least the upon operation of said generator, anodeof said tube is mounted, i primary il comprising a d bl i di f anelectrically conductive secondary transformer coil helicale1etrica11y.conductive tubing, electrically coupled to said primary coiland disposed one of said windings being formed with an inl t outsidesaid first-named enclosure but connected through which a coolant may besupplied to said f i tubing, and said coils beingelectrlcally-conductlve tubing for conthe other of said windings beingformed with an outi f let through which a coolant may be drained fromsald P i .coll bemg connected at one end to a said tubing. iiilfseiiiiil iii iin i iilinifi i ifiif fifi boggtesiiigl inlet and saidoutlet being at ground .fi qavity igg coolalllltflthereimm,

sai cavi errm 1n mo 13. Sputter ng apparatus as claimed in cla m 12, theg z tubeg E i li gag 3 over wh lf y g meal ls lndudmg electron: 3 20.Sputtering apparatus as claimed in claim 19, 15 mounted 111 5 hfmsmgOperatlvely connect said wherein said primary coil comprises a doublehelix comgelleratol and Sald P f 'y coil, and posed of one tubularconduit for conducting coolant to the mounting 531d tube Includes ablock 111 Whlch said block and a second tubular conduit for conductingthe anode end of Said tube is mounted, coolant from said block, saidconduits being helically said block has a passage therethrough forcoolant, wound about one another. and said windings are connected tosaid passage to 21. Sputtering apparatus comprising deliver coolant intoand exhaust coolant from said an evacuatable enclosure, block. a targetsupport mounted in said enclosure, 14. Sputtering apparatus comprising asecond enclosure, an evacuatable enclosure, a block mounted in saidsecond enclosure, a target support in said enclosure, a radio frequencygenerator mounted outside of said radio frequency signal generatingmeans, second enclosure, a transformer comprising a primary winding anda electronic amplifying mechanism mounted in said Secondary indin secondenclosure and connected to said generator, said secondary winding beingmounted outside said enand including an electronic amplifier tubemounted closure but in operative relation thereto to transmit on saidblock to extend into a cavity in said block, radio frequency energy intosaid enclosure upon means for cooling said amplifier tube and saidtarget operation of said generating means, support comprising first andsecond electronically said windings each being electrically conductiveand conductive conduits, one of said conduits being coneach comprising adouble wound helical electricallynected at one end to a coolant supplyand at its conductive tube, opposite end to said cavity to supplycoolant to said the two tubes of the primary and secondary windingscavity, and being wound between its ends into a being integral, primarytransformer coil electrically connected to one end of the secondarywinding constituting an inlet said amplifier tube, and the other of saidconduits for coolant, and being connected at one end to said cavity todrain one end of the primary winding constituting an outlet coolant fromsaid cavity and being wound into a for draining coolant from bothwindings. secondary transformer coil electrically coupled to 15.Sputting apparatus as claimed in claim 14, wheresaid primary transformercoil and then extending in the windings are grounded at inlet andoutlet. into juxtaposition to said evacuatable enclosure and 16.Sputtering apparatus as claimed in claim 14, whereoperatively connectedthereto and then being interwound helically with said secondarytransformer coil, and having a discharge port at its end. 22. Sputteringapparatus as claimed in claim 21,

' wherein both the supply end of said first conduit and the dischargeend of said second conduit are grounded. 23. A radio-frequency amplifierassembly, comprising a housing for an amplifier tube having at least ananode, a cathode, and a grid, an anode resonant coil mounted on saidhousing, a'longitudinally slotted electrically conductive cylindersurrounding said coil but spaced radially therefrom, anelectrically-conductive shield spaced from and surrounding saidcylinder, said cylinder constituting one electrode of a capacitor forsaid amplifier tube, and said shield forming the other electrode of saidcapacitor, a coolant manifold secured to said shield and connected to acoolant supply and to a coolant drainage tube,

said coil being an electrically conductive conduit for 20 S. S. KANTER,Assistant Examiner conveying coolant and having both its ends extendingthrough said slot to said manifold for sup- 1 coil to adjust thefrequency of the signal developed by said coil.

References Cited UNITED STATES PATENTS 3,562,142 2/1971 Lamont 204-2983,525,680 8/1970 Davidse etal. 204-192 3,471,396 10/1969 Davidse204--298 3,347,772 10/ 1967 Laegreid et al. 204298 3,594,295 7/ 1971Meckel et al 204I2'98 2,731,585 1/ 1956 Rousseau 315-248 r 2,749,5006/1956 Eagan 322- 28 2,907,944 10/ 1959 .Hume 321"69 Hoffman 317--,-2

JOHN H. MACK, Primary Examiner

